Added hacks for SIMD rvec/load store in lincs & bondeds

Added hacks for SIMD rvec/load store in lincs & bondeds

We have added proper gather/scatter operations to work on
rvecs for all SIMD architectures, but that will not make it into
Gromacs-5.1. Since Berk already wrote a few routines to use
maskloads at least for AVX & AVX2, this is a bit of a hack to
get the performance benefits of that code already in Gromacs-5.1
(for AVX/AVX2), without altering the SIMD module. This is definitely
a hack, and the code will be replaced once the extended SIMD
module is in place.

Change-Id: I385acb5f989b2ecf463948be84947fe1f6dfd19b